OCI questions from a newbie

My late mother's Indian passport has not got her surname under name of bearer, but she has signed the photograph using her initials and surname.

My wife was born in Delhi and has a certificate of registration as a citiezen of UK issued in 1982, with her full name and country of birth (India). Her old Indian passport (expired in 1985) has not been surrendered and has never been used for travel. Her name on the front page is without surname, but she has also signed her photo using her full name, including her maiden surname.

I have the marriage certifice (issued in the UK).

I will be gratefull for any help on the following questions:

1 Have I got enough evidence to apply for OCI for myself, my wife and my children (all over 18)

2 Will there be any problem with surnames not appearing on the first page of the passports being surrendered?

3 if my older brother wishes to apply for OCI using my mothers passport as evidence at a future date, what should I do as I gather I will have to surrender my mothers and my wifes passports?

4 What documents do I need to support my OCI application?

5 Is there a cheaper option for applying as a family?

Thanks in advance for your help

1, 4 - also see Documents Required and Other Supporting Documents

2. Can't say for sure. Shouldn't not be. Please attach a letter explaining.

3. I don't think there is any need to surrender your mothers passport now as she is dead. HCI not retain any originals.

5. There is no cheaper option. Each applicant needs to pay the applicable fee.

3. Mother's death certificate should be included too.